Sweating has an important physiological function concerned with both temperature and fluid balance. Hypohidrosis is uncommon and rarely recognized by the patient. It usually represents damage to the central nervous system or peripheral nerves. Hyperhidrosis may be a feature of general medical diseases such as thyrotoxicosis and fevers. It may also be due to damage of the central of peripheral sympathetic nerves. Localized hyperhidrosis tends to occur on the palms, the soles, the axillae and, to a lesser extent, the face. Treatment of local hyperhidrosis with topical aluminium salts, or with topical or oral anticholinergics, may help some patients but surgery may be indicated in those with severe hyperhidrosis.